Incident Response Guide: Black Basta Ransomware

Incident Triage Steps

Within the first 30 minutes, your priority is to confirm the incident, assess its scope, and determine if data exfiltration occurred. Black Basta typically operates as part of a broader intrusion, often following initial access via phishing, exploited vulnerabilities (like QakBot or recent Microsoft Exchange flaws), or compromised credentials.

Immediate Actions:

1. Isolate the First Identified System: Physically disconnect or logically isolate the first reported machine from the network. Do not shut it down yet, as this destroys volatile evidence.
2. Identify the Ransom Note: Black Basta drops a ransom note named readme.txt on the desktop and in affected directories. The note’s content and the .basta file extension appended to encrypted files are primary indicators.
3. Determine Scope: Query your EDR solution or perform a rapid manual check on key servers and workstations for:
   • The presence of readme.txt files.
   • Files with the .basta extension.
   • Suspicious processes like cmd.exe or powershell.exe spawning from unusual parent processes or writing to large numbers of files.
   • Check critical servers first, especially file servers, domain controllers, and backup systems.
4. Check for Exfiltration: Black Basta actors almost always exfiltrate data prior to encryption. Immediately review outbound network logs and data loss prevention (DLP) alerts from the last 30 days for:
   • Large, unusual data transfers to unfamiliar external IP addresses or cloud storage domains.
   • Connections to known or suspected Black Basta command-and-control (C2) infrastructure (check your threat intelligence feeds for recent IOCs).
   • Look for tools associated with their TTPs, such as Rclone, FileZilla, or MegaSync, which may have been deployed for data theft.

Evidence Collection

Before initiating containment or remediation, preserve forensic evidence. This is critical for understanding the attack and potentially aiding law enforcement.

Volatile Data (From Live Systems):

• Memory Dump: Use a trusted, pre-installed forensic tool to capture a full memory dump of at least one infected, isolated system.
• Process List & Network Connections: Execute commands like tasklist /v, netstat -anob, and wmic process get caption,commandline,processid,parentprocessid from a trusted utility (e.g., from a write-blocked USB drive). Black Basta processes may masquerade with legitimate names.
• Precise Timelines: Record the exact time the encryption started and when the ransom note appeared.

Persistent Artifacts (Collect from multiple systems):

• Ransom Note: Preserve the readme.txt file.
• Encrypted Files: Keep a sample of encrypted files (with the .basta extension).
• System Logs: Export relevant Windows Event Logs, especially Security (Event ID 4688 for process creation), System, and PowerShell logs. Look for events related to:
  • Service creation (e.g., for the ransomware binary).
  • Windows Defender or antivirus disablement.
  • Volume Shadow Copy deletion (vssadmin delete shadows).
• Registry: Export registry hives, particularly focusing on:
  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run and RunOnce
  • HKLM\SYSTEM\CurrentControlSet\Services\ (for new or suspicious services)
  • User autorun keys.
• Disk Artifacts: Collect the ransomware executable if found, often in C:\Windows\Temp\, C:\Users\Public\, or AppData\Local\Temp\. Also, collect any suspicious batch files (*.bat), PowerShell scripts (*.ps1), or living-off-the-land binaries (like schtasks.exe or bcdedit.exe) with recent timestamps.

Containment Procedures

Containment aims to stop the ransomware from spreading while preserving evidence.

1. Network Segmentation:

   • Immediately segment or isolate entire network blocks where infection is confirmed. If possible, place all affected subnets into a quarantined VLAN with no internet or internal access.
   • Disable all inter-VLAN routing and SMB (ports 139/445) traffic from infected segments.
   • Isolate or take offline critical infrastructure like domain controllers, backup servers, and SAN/NAS devices that are not yet encrypted but may be in the same network segment.

2. Credential Reset:

   • Assume all credentials on compromised systems are breached. Black Basta actors use tools like Mimikatz to harvest credentials.
   • Initiate a mandatory reset for all domain administrator and local administrator passwords.
   • Reset service account passwords and Kerberos tickets (consider a domain-wide Kerberos ticket reset if domain controllers are suspected to be compromised).
   • Implement multi-factor authentication (MFA) immediately for all remote access and administrative portals if not already enabled.

3. C2 and Traffic Blocking:

   • Update firewall and proxy rules to block communications to known Black Basta C2 IPs and domains from your threat intel feed.
   • Block outbound connections on common exfiltration ports (e.g., FTP, SFTP, Rclone-related ports) from non-business-critical systems.
   • Consider temporarily blocking all outbound traffic from contained segments except to approved management and security tooling IPs.

Eradication and Recovery

Eradication must be thorough to prevent re-infection. Recovery should use verified clean backups.

1. Complete Eradication:

   • Do not simply delete the ransomware binary or decrypt files. A full system rebuild is strongly recommended, as the system is fundamentally compromised.
   • Follow the detailed, step-by-step instructions in the Black Basta Removal Guide for per-system cleanup if rebuilding is not immediately possible. This includes killing malicious processes, removing persistence mechanisms, and deleting attacker tools.
   • After cleanup, perform a full anti-malware scan with updated signatures from all endpoints in the affected environment.

2. Secure Recovery from Backups:

   • Verify your backups are clean and unencrypted before restoration. Ensure the backup system/media was not connected to the network during the attack.
   • After rebuilding host operating systems from trusted gold images, restore user and application data from the verified clean backups.
   • Before reconnecting restored systems to the production network, ensure all critical patches are applied, credentials have been changed, and endpoint security is installed and updated.

3. Verifying a Clean State:

   • Before returning to normal operations, monitor the restored and cleaned systems in an isolated network segment for 24-48 hours.
   • Use your EDR and SIEM to look for any residual malicious network calls, processes, or registry changes.
   • Validate that no new .basta files appear and that system logs show no further malicious activity.

Lessons Learned Checklist

After containment and recovery, conduct a formal post-incident review.

• Initial Access Vector: How did Black Basta gain entry?
  • Was it a phishing email? Which user was targeted, and what was the lure?
  • Was it an exploited vulnerability (e.g., in VPN, email server, public-facing app)? Were the relevant patches available but not applied?
  • Was it compromised remote desktop (RDP) or other remote access credentials?
• Control Failures: What security controls did not work as intended?
  • Email Filtering: Did it fail to block the malicious email or attachment?
  • Endpoint Protection: Did antivirus or EDR fail to detect the initial payload, lateral movement tools, or the ransomware binary? Were they disabled?
  • Patch Management: Were the systems vulnerable due to unpatched software?
  • Backup Strategy: Were backups offline/immutable? Were they successfully tested before the incident?
• Detection Gaps: Where were the blind spots?
  • Did your SIEM or network monitoring fail to alert on the C2 communication, large data exfiltration, or suspicious internal lateral movement (e.g., PsExec, WMI)?
  • Was there a delay between initial compromise and ransomware deployment that went unnoticed?
• Improvement Plan: Based on the above, what will you change?
  • Immediate: Implement application allowlisting, enforce MFA everywhere, establish immutable/air-gapped backups.
  • Technical: Enhance logging and alerting for specific Black Basta TTPs (see the Black Basta Detection Guide). Review and harden internet-facing systems.
  • Process: Update incident response playbooks. Conduct user security awareness training focused on the identified initial access method. Schedule mandatory backup restoration drills.

For more information on this threat, refer to the Black Basta Overview.